Ground fault circuit interrupter with reverse wiring protection

ABSTRACT

A new type of switching mechanism for a ground fault circuit interrupter (GFCI) with reverse wiring protection preferably includes two pairs of fixed contact holders, each member of each pair having at least one fixed contact at one end; a pair of movable contact holders, each having an end having one or more of movable contacts, each movable contact being arranged for contacting one of the fixed contacts; and a movable assembly that moves between first and second positions, wherein the first position is a position in which each of the contacts of the fixed contact holders makes contact with one of the contacts of the movable end of one of the movable contact holders, and wherein the second position is a position in which the contacts of the fixed contact holders are separated from the contacts of the movable contact holders.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/294,714, filed on Nov. 15, 2002, commonly assigned, andincorporated herein by reference in its entirety. U.S. patentapplication Ser. No. 10/294,714, in turn, claims priority of ChinesePatent Application No. 02131108.0, filed on Oct. 9, 2002, which isincorporated also herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ground fault circuit interrupter(GFCI) for load ground-fault protection. More specifically, theinvention relates to a GFCI receptacle utilizing an electromagnetictripper and providing reverse wiring protection.

2. Discussion of Related Art

Ground fault circuit interrupter (GFCI) devices are designed to trip inresponse to the detection of a ground fault condition at an AC load. Forexample, the ground fault condition may result when a person comes intocontact with the line side of the AC load and an earth ground at thesame time, a situation that can result in serious injury. The GFCIdevice detects this condition by using a sensing transformer to detectan imbalance between the currents flowing in the line and neutralconductors of the AC supply, as will occur when some of the current onthe line side is being diverted to ground. When such an imbalance isdetected, a circuit breaker within the GFCI device is immediatelytripped to an open condition, thereby opening both sides of the AC lineand removing all power from the load.

A GFCI generally includes a housing, a tripper, a reset button, a testbutton, a mounting strap with grounding strap and banding screw, a pairof movable contact holders with contacts, a pair of fixed contactholders with contacts, and a control circuit. Currently, GFCIs arewidely used to prevent electric shock and fire caused by a ground fault.

In the past, a GFCI receptacle generally utilized a mechanical actuator,which limited the performance of such products, especially insofar asthese GFCIs did not provide reverse wiring protection. In addition,these mechanical GFCIs required high standards in the quality of theparts and assembling work. Examples of mechanical GFCIs include thosedisclosed in U.S. Pat. No. 5,933,063 and U.S. Pat. No. 4,802,052.

The GFCI shown in U.S. Pat. No. 6,252,407 B1 has reverse wiringprotection, but it is a visual alarm indicator signaling a miswiringcondition to the installer, and if miswired (despite the visual alarmindicator) by connecting the line to the load, the GFCI can still bereset. Under such circumstances, an unknowing user, faced with a GFCIthat has been miswired, may press the reset button, which, in turn, willcause the GFCI to be reset without reverse wiring protection available.And, such a GFCI that has been reset can very easily be tripped again inevents like lightning strikes.

The design of these GFCIs allows two means of connection: the load canpass through the entry ports of the face portion or can alternativelyconnect through the load binding screws. Consequently, an installer oruser can still mistakenly connect the line and the load in a reversedirection. When this occurs, without reverse wiring protection, the GFCIwill function just as a common (non-GFCI) receptacle.

There is a need for a GFCI that, in order to improve the safety featuresof the receptacles, is capable of providing reserve wiring protection;is highly responsive; is convenient to assemble; and has improvedfunctionality.

SUMMARY OF THE INVENTION

It is an object of the pesent invention to provide a GFCI circuit thathas the above characteristics.

The ground fault circuit interrupter (GFCI) according to the presentinvention comprises a pair of first contact holders, each having acontact at one end; a pair of movable contact holders, each having afixed end and a movable end, each of the movable ends having a contact;a movable assembly that moves between a first position and a secondposition, wherein the first position is a position in which each of thecontacts of the first contact holders makes contact with one of thecontacts of the movable end of one of the movable contact holders, andwherein the second position is a position in which the contacts of thefirst contact holders are separated from the contacts of the movablecontact holders; an electromagnetic resetting component, which, whenenergized, causes the movable assembly to be in the first position; anelectromagnetic tripping component, different from the electromagneticresetting component, which, when energized, causes the movable assemblyto be in the second position; and a control circuit, which, upondetection of a fault condition, energizes the electromagnetic trippingcomponent, and which, after a reset switch is activated, energizes theelectromagnetic resetting component.

One particular object of an embodiment of the present invention is toprovide a GFCI receptacle with reverse wiring protection thatincorporates an electromagnetic tripper and a corresponding controlcircuit.

The GFCI receptacle according to a first embodiment of the presentinvention comprises an electromagnetic tripper, a rear portion, acentral body, a face portion, a test button, a reset button, anindicator, a mounting strap with a grounding strap and a binding screw,a pair of movable contact holders having one end fixed and the other endable to freely bias, a pair of fixed contact holders mounted on thecentral body, and a control circuit.

Because the tripper is electromagnetic, the GFCI receptacle carries outthe breaking and making operation through the interaction of therelevant electromagnetic forces produced by the trip coil (J₁), theclosing coil (J₂) produces, and the permanent magnet. Furthermore, byusing the magnetic force of the permanent magnet to provide a retentiveforce on the tripper, the operating sensitivity is improved, and theGFCI is more energy efficient.

According to another feature of the invention, the GFCI is provided withreverse wiring protection in that the control circuit is de-energizedwhen the GFCI is miswired by connecting the line to the load so that theGFCI receptacle can not be reset. When the GFCI is miswired, the faceportion, particularly at the entry ports and the ground-prong-receivingopenings that accommodate the three-wire plugs, is without a flow ofelectricity, which provides additional safety feature for human use.

A further object of the present invention is to provide anelectromagnetic tripper that is electronically controlled. In such anembodiment (for example, the implementation shown in FIG. 10), thetripper comprises a permanent magnet, a coil framework, a trip coil, aclosing coil, a plunger, a trip spring, a movable bracket, a balanceframe, and a small spring providing a contact force for the movablecontact holders. When the reset button is depressed, the closing coilwill be energized and will produce an electromagnetic force that workswith the magnetic force of the permanent magnet to act on the plunger toovercome the returning force of the trip spring and certain frictionalforces, thereby closing the tripper, and the magnetic force of thepermanent magnet maintains the tripper in the closed condition. Becausethe plunger and the movable bracket are coupled, the movement of theplunger directly drives the movable bracket to move in the samedirection, and the movement of the movable bracket causes the balanceframe to move. The movement of the balance frame lifts the removablecontacts against the fixed contacts through the special shape of themovable contact holder (the movable contact holder has a V-shapedgroove, and when it is in the tripping state, the bracket of the balanceframe moves into the V-shaped groove). When the tripper is in the closedstate, the movable contact connects with the fixed contacts, and thesmall spring associated with the balance frame provides a contact forceto maintain good contact, thereby maintaining the GFCI receptacle in thenormal operating condition.

When the GFCI receptacle of the above embodiment is energized, if aground fault occurs at the load or there is a factitious fault current,the control circuit will gate a silicon controlled rectifier (SCR) intoconduction to energize the trip coil. The trip coil will then produce anelectromagnetic force in the direction which repels the magnetic forceof the permanent magnet. The electromagnetic force and the returningforce of the trip spring act on the plunger, thereby making the tripperopen quickly.

Still another object of the present invention is to provide a specialcontrol circuit which mainly comprises a DC power source, integratedamplification circuit, sensing circuit, trip circuit, reset circuit, andtest circuit. In one embodiment of the invention in which these objectsare satisfied, four diodes form a full-wave bridge rectifier circuit.After the AC from the line is commutated by the rectifier circuit, therewill be DC on the output terminal of the rectifier circuit. Thisembodiment includes an integrated amplification circuit, which may be aspecial IC (for example, of the type RV4145A or RV2145). The sensingcircuit may include a sensor that comprises a sensing transformer and aneutral transformer. The AC line and neutral conductors pass through thetransformers. In operation, the sensing transformer serves as adifferential transformer for detecting a current leakage between theline side of the load terminal and an earth ground, while the neutraltransformer detects current leakage between the neutral side of the loadterminal and an earth ground. When an imbalance between the currentsflowing in the line and neutral conductors of the AC supply is detected,a circuit breaker within the GFCI device is immediately tripped to anopen condition, thereby opening both sides of the AC line and removingall power from the load. In the reset control circuit, the reset switchis connected to a silicon controlled rectifier (SCR). When the resetswitch is closed, the SCR will be gated into conduction and will cause aclosing coil connected with the SCR to be energized to thereby reset theGFCI. Simultaneously, a capacitor is connected to the reset switch tokeep the closing coil energized for an instant. In this way, it preventsthe closing coil from being burned out in the event that the currentflowing through the closing coil is too large and the energized time istoo long.

The power supply of the control circuit is connected to the AC supply ofthe GFCI, so when the GFCI is energized, the control circuit is alsoenergized. However, if the GFCI is miswired by connecting the line tothe load, the control circuit is de-energized, and the GFCI will not beable to be reset, achieving the reverse wiring protection function.Because the reset of the GFCI is electronically controlled, theoperation is more convenient, and the action is more sensitive comparedto GFCIs using mechanical means.

In a further embodiment of the invention, the movable contact holders,the movable assembly, and the fixed contacts are arranged so as toprovide two separate contact points between movable contacts and fixedcontacts on each side (phase and neutral) of the GFCI. In onesub-embodiment, the single movable contact holder on each side isreplaced with two movable contact holder elements, each having aV-shaped bend, the two movable contact holder elements being placedagainst each other with the V-shaped bends arranged opposite each other.One end of each movable contact holder element has a movable contact,and the other end is joined with the other end of the other movablecontact holder element and connected to a conductor coupled to one sideof the line (i.e., either phase or neutral). In this arrangement, themovable contact holder elements remain together, and the movablecontacts do not make contact with the fixed contacts, in the trippedstate, while the movable contact holder elements are separated (by themovable assembly), and contact is made, when the GFCI is reset.

In a second sub-embodiment, the movable contact holder is mounted on themovable assembly and is connected to a flexible conductor on one end.The other end of the movable contact holder is provided with the twomovable contacts, which make contact with the two fixed contacts whenthe movable assembly is in a first (closed) position and does not makecontact when the movable assembly is in a second (tripped) position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further detail in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a perspective view of a GFCI according to an embodiment of thepresent invention;

FIG. 2 is a side view, in longitudinal section, of the GFCI in FIG. 1showing the relative positions of the assembly in the tripped condition;

FIG. 3 is a perspective view of the GFCI in FIG. 1 with the face portionremoved, showing the internal configuration of the GFCI of FIG. 1;

FIG. 4 is an exploded, perspective view of the GFCI in FIG. 1;

FIG. 5 is an exploded view of the electromagnetic tripper of the GFCI inFIG. 1;

FIG. 6 is a perspective view of the trip actuator and a portion of theGFCI in FIG. 1, showing the assembled relationship of the trip actuator;

FIG. 7 is a detailed, sectional side view of the GFCI in FIG. 1 in thetripped condition;

FIG. 8 is another detailed, sectional side view of the GFCI in FIG. 1 inthe tripped condition from a different perspective from FIG. 7;

FIG. 9 is a detailed, sectional side view of the GFCI in FIG. 1 in theclosed condition;

FIG. 10 is a schematic diagram of a circuit of the GFCI according to anembodiment of the present invention;

FIG. 11 is a detailed, sectional side view of the GFCI in the trippedcondition, according to a further embodiment of the invention;

FIG. 12 is a detailed, sectional side view of the GFCI in the trippedcondition, according to a further embodiment of the invention;

FIGS. 13A-13C conceptually depict a split version of a fixed contactholder for use in connection with the embodiments shown in FIGS. 11, 12,and 15;

FIG. 14 is a modified version of the circuit diagram of FIG. 10 showingthe split version of the fixed contact holder as in FIGS. 13A-13C; and

FIG. 15 is a detailed, sectional side view of the GFCI in the trippedcondition, according to a modification of the embodiment of theinvention shown in FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a view of the exterior of a GFCI according to an embodimentof the present invention. The GFCI receptacle has a housing consistingof a face portion 30, a central body 20 (not shown in FIG. 1, butappearing, for example, in FIG. 2) and a rear portion 10. The faceportion 30 has entry ports 31 for receiving normal or polarized prongsof a male plug of the type normally found at the end of a lamp orappliance cord set (not shown), as well as ground-prong-receivingopenings 32 to accommodate three-wire plugs. The GFCI receptacle alsoincludes a mounting strap 40 for fastening the receptacle to a junctionbox, and the mounting strap 40 has a threaded opening to receive a screw113 for connection to an external ground wire. A test button 50 extendsthrough an opening in the face portion 30 of the housing. The testbutton 50 can be activated to test the operation of thecircuit-interrupting portion disposed in the device. A reset button 60,which forms a part of a reset portion of the device, extends through anopening in the face portion 30 of the housing. The reset button is usedto activate a reset operation, which reestablishes the electricalcontinuity in the open conductive paths. Electrical connections toexisting household electrical wiring are made via binding screws 110 and111, where the binding screw 110 is a line phase connection, and thebinding screw 111 is a load phase connection. It should be noted thattwo additional binding screws (not shown) are located on the oppositeside of the GFCI receptacle. An indicator 114 (generally alight-emitting diode (LED)) extends through the opening of the faceportion 30 of the housing. When the GFCI is normally energized, theindicator is illuminated.

The GFCI illustrated in FIG. 1 may be rated, for example, at 20 A. Thepresent invention also provides other types of GFCIs, at variousamperage ratings, and these GFCI receptacles all have twoconfigurations, one without an indicator and the other with anindicator. Both configurations operate under the same principle.Therefore, the description below, while specifically for the rated 20 AGFCI with an indicator, also applies to the other types of GFCIs.

Referring to FIG. 2, the assembled relation of the GFCI receptacle isshown in the tripped condition. All of the subassemblies and componentparts are fixed mainly to the housing (consisting of the face portion30, the central body 20 and the rear portion 10) of the GFCI. Anelectromagnetic tripper is built into the GFCI receptacle of the presentinvention. A permanent magnet 71 is set into one end of a coil framework70, and covered by an outside shield cover 72. One end of the shieldcover 72 is abutted against one side of the rear portion 10. The coilframework is mounted on a circuit board 90 by four binding pins. Acircular core of sensor framework 80 is set into a fixed hole of thecircuit board 90, and the sensor framework 80 is also mounted on thecircuit board 90 by four binding pins. The U-shaped portion of thesensor framework 80 is set into a corresponding groove on the centralbody 20. There is an isolation layer 82 between the sensing transformer81 and the neutral transformer 83. The sensing transformer 81 may becomposed, for example, of high original magneto-conductivity magneticalloy flakes and enamel-insulated wire. The neutral transformer 83 may,for example, be composed of ferrite (high μ value, large temperaturemodulus) and enamel-insulated wire. A plunger 75 is molded into the sideof a movable bracket 79. The elasticity of a trip spring 76 makes oneside of the movable bracket 79 abut against the sensor framework 80 inthe trip condition. The upper side of the movable bracket 79 has acentral hole, and a small spring 78 is set into it to prop up balanceframe 77 and to provide a contact force for the contacts. Through theinteraction of the magnetic force of the permanent magnet 71 and theelectromagnetic force that the trip coil 74 or the closing coil 73produces in an energized condition, the plunger 75 activates the movablebracket 79 to drive the balance frame 77 to move back and forth in theU-shaped groove, as shown. Contact strap 61 is molded into the undersideof reset button 60. One end of reset spring 62 props up the reset button60, and the other end presses onto mounting strap 40. The test button 50is propped up by test strap 51. In one embodiment of the GFCI, thisarrangement ensures that the top surface of the test button 50 issubstantially level with the surface of the face portion 30 untilpressed.

Referring to FIG. 3, a pair of fixed contact holders 100A and 100B withcontacts 101 are mounted on the central body 20. A mounting strap 40with grounding strap 41 and binding screw 113 is set onto the centralbody 20, and the face portion 30 impacts it. One end of a test strap 51is set into a corresponding slot on the central body 20; its outsideabuts against the inside of the fixed contact holder 100B; and the otherend of the test strap 51 can flexibly contact with the test resistor 52(shown, e.g., in FIG. 4). The contact strap 61, which is molded into theunderside of the reset button 60, can flexibly contact the binding pins63 through the action of the reset spring 62, which props up the resetbutton 60, thus controlling the reset action of the tripper.

FIGS. 2 and 3 also show the physical relationship among the mountingstrap 40, the central body 20, and coil framework 70 (including both thetrip coil 74 and the closing coil 73). In particular, these figures showthat mounting strap 40 is physically separated from coil framework 70 bycentral body 20. Central body 20 may be constructed of, for example, aninsulating material. Central body 20 may thus be constructed such thatmounting strap 40 does not define a path of a magnetic field generatedby either trip coil 74 or closing coil 73, i.e., such that mountingstrap 40 is magnetically isolated from trip coil 74 and closing coil 73.

FIG. 4 is an exploded view of the GFCI receptacle according to anembodiment of the present invention. As shown, the GFCI receptaclecomprises a rear portion 10, a central body 20, a face portion 30, amounting strap with a grounding strap 41 and a binding screw 113, a pairof movable contact holders 102A and 102B with contacts 103, a pair offixed contact holders 100A and 100B with contacts 101, an actuator, areset mechanism, a test mechanism and a control circuit. The actuatorcomprises a coil framework 70, a permanent magnet 71, a shield cover 72,a closing coil 73, a trip coil 74, a plunger 75, a trip spring 76, abalance frame 77, a small spring 78 providing a contact force, a movablebracket 79, and four binding pins 701. The reset mechanism includes areset button 60 molded with a contact strap 61 (shown in FIG. 3), areset spring 62, and a reset binding pin 63. The test mechanism includesa test button 50, a test strap 51, a test resistor 52, a sensorframework 80, a sensing transformer 81, an isolation layer 82, and aneutral transformer 83. In addition, the line terminal 104 is connectedto the line wire by the line binding screw 110 associated with thepressure plate 105; the load can also be connected to the GFCI throughthe load binding screw 111 and a corresponding pressure plate 105. Allsubassemblies and component parts are assembled as shown in the drawing.The rear portion and the face portion of the housing are connectedtogether by four fastening screws 115. The reset button 60 extendsthrough the reset opening 33 on the face portion 30 of the housing. Thetest button 50 extends through the test opening 34 on the face portion30 of the housing. One of the ends of each of the movable contactholders 102A and 102B passes through the sensor framework 80 and issoldered onto the circuit board 90. The other end of each can movefreely.

FIG. 5 is an exploded view of the electromagnetic tripper of FIG. 4.Because the plunger 75 is molded onto the movable bracket 79, themovement of the plunger 75 can drive the sliding boards 79A and 79B tomove back and forth in the runners 70A and 70B, respectively. Themovement of the movable bracket 79 drives the balance 77 to move toperform the operation of breaking contact and making contact (betweenthe fixed and movable contacts). The assembled relationship of theelectromagnetic tripper is further shown in FIG. 6.

Referring now to FIGS. 7, 8, and 9, when the trip coil 74 or the closingcoil 73 is energized, it produces a corresponding electromagnetic forceto interact with the magnetic force of the permanent magnet 71 and actson the plunger 75. In this manner, the plunger 75 drives the balanceframe 77 back and forth. In the trip condition, when trip coil 74 isenergized, the bracket 77A of the balance frame 77 is set into theV-shaped groove A of the movable contact holder 102A, and the bracket77B of the balance frame 77 is set into the V-shaped groove B of themovable contact holder 102B, as shown in FIGS. 7 and 8. As a result, thecontacts 101 and 103 are separated from each other.

On the other hand, when the closing coil 73 is energized, the plunger75, under the magnetic force, drives the balance frame 77 to move suchthat the brackets 77A and 77B on the two sides of the balance frame 77force the movable contact holders to bias. When one end of the plunger75 is attracted to and pressed against the permanent magnet 71 (i.e.,when closing coil 73 is energized), the brackets on two sides of thebalance frame 77 are located on the plane position of the V-shapedgroove and hold the contacts 103 of the movable contact holders againstthe contacts 101 of the fixed contact holders, as shown in FIG. 9. Thesmall spring 78 provides a contact force for the contacts 103 and 101 tohelp maintain the contact. The special shape of the movable contactholders 102A and 102B prevents the plunger 75 from being attracted andclosed in the event of improper operation and also contributes to makingthe tripper act quickly.

FIG. 10 shows a general GFCI circuit of the present invention. DiodesD₁-D₄ form a rectifying circuit, converting the AC input to a DC output.The junction of D₁ and D₂ and the junction of D₃ and D₄ form the ACinput terminals and are connected to the line of the GFCI. The junctionof D₂ and D₄ forms one terminal for the DC output, and this junction isreferred to as the “ground” hereinafter. The junction of D₁ and D₃ formsthe other terminal of the DC output and connects with the resistor R₄.The other end of R₄ is connected to the capacitor C₅. The other end ofC₅ is then connected to the “ground”. In the exemplary 20 A-rated GFCIdevice, an electrical voltage of approximately 26V formed between thetwo ends of C5 serves as a DC voltage for the circuit.

As discussed above, the exemplary ground fault circuit interrupter has asensor, a trip circuit, a test circuit and a reset circuit. The sensorhas a sensing transformer N₁ and a neutral transformer N₂, as shown inFIG. 10. The AC line and the neutral conductors pass through bothtransformers. The two ends of a sensing coil of sensing transformer N₁connect to opposite ends of the capacitor C₀. One end of the sensingcoil of N₁ serially connects to the capacitor C₁, the resistor R₅, andthen the terminal 1 of the IC (which, as discussed below, may include anamplifier circuit), and the other end of the sensing coil of N₁ connectsto the terminal 3 of the IC, forming a transformer-coupled circuit thatreceives differential voltage inputs. The feedback resistor, R₁,connects to the terminal 1 of the IC at one end and to the terminal 7 ofthe IC at the other end. The magnitude of resistance at R₁ determinesthe amplification of the IC, that is, the threshold value for thetripping action of the GFCI.

The neutral transformer N₂, the capacitor C₂, and the capacitor C₃ formthe neutral ground-fault protection circuit. The two ends of the sensingcoil of neutral transformer N₂ are connected to opposite ends of thecapacitor C₂. One end of the sensing coil of N₂ is further connected tothe capacitor C₃ and the other end of the sensing coil of N₂ isconnected to the “ground”. The other end of the capacitor C₃ isconnected to the terminal 7 of the IC.

Given the above-described apparatus, neutral ground-fault protectionoccurs as follows: The transformers N₁ and N₂ form a sigmoid-waveoscillator with a transformer-coupled oscillating frequency of 5 kHz.When a neutral ground fault occurs, this oscillator starts to oscillate.When the magnitude of the oscillation reaches the IC threshold value,then the terminal 5 of the IC delivers a signal, putting the tripper inmotion and the GFCI breaks contact. In other words, in operation, thesensing transformer (N₁) serves as a differential transformer fordetecting a current leakage between the line side of the load terminaland an earth ground, while the neutral transformer (N₂) detects currentleakage between the neutral side of the load terminal and an earthground. In the absence of a ground fault condition, the currents flowingthrough the conductors will be equal and opposite, and no net flux willbe generated in the core of the sensing transformer (N₁). In the eventthat a connection occurs between the line side of the load terminal andground, however, the current flowing through the conductors will nolonger precisely cancel and a net flux will be generated in the core ofthe sensing transformer (N₁). When the flux increases beyond apredetermined value, it will give rise to a potential at the output ofthe sensing transformer (N₁), which is applied to the inputs 1 and 3 ofthe IC and trip circuit, sufficient to produce a trip signal on theoutput terminal 5. If the ground fault condition results from theneutral side of the load terminal being connected to ground, a magneticpath is established between the sensing transformer (N₁) and the neutraltransformer (N₂). When this occurs, a positive feedback loop is createdaround an operational amplifier within the IC and trip circuit, and theresulting oscillations of the amplifier (IC) will cause the trip signalto appear on the output terminal 5.

As discussed above, resistor R₁ is utilized as a feedback resistor forsetting the gain of the circuit and, hence, its sensitivity to groundfaults. The capacitors C₁ and C₃ provide AC input coupling. In theabsence of a ground fault condition, no output is produced by theamplifier (IC) and trip circuit on the output terminal 5. Under thesecircumstances, the negative pole of a silicon controlled rectifier (SCR)VD₇ is connected to the ground of the full-wave bridge rectifier formedby D₁-D₄ (described in detail above), and the positive pole of the SCRVD₇ is connected to trip coil J₁ to maintain it in a non-conductingstate. Similarly, the negative pole of an SCR VD₅ is connected to theground of the full-wave bridge rectifier, and the positive pole of theSCR VD₅ is connected to closing coil J₂ to maintain it in anon-conducting state. Since the current drawn by the resistor R₄ andamplifier and trip circuit is not sufficient to operate the trip coil,the plunger remains motionless.

The occurrence of a ground fault condition causes the amplifier and tripcircuit to produce an output on terminal 5 of the IC, which is appliedto the gate terminal of the SCR VD₇, thereby rendering the SCR VD₇conductive. This produces a short circuit across the outputs of thefull-wave bridge rectifier, thereby providing a low-impedance path forcurrent to flow through the trip coil J₁. The resulting movement of theplunger causes the movable contacts to move to the open position,thereby removing power from the entry ports of the face portion and theload terminals. This ensures that the GFCI receptacle remains in acondition to detect a ground fault condition immediately upon beingreset.

The reset switch RESET, the resistors R₂ and R₃, the capacitors C₆ andC₇, the SCR VD₅, the closing coil J₂, and the breaking switch K form thereset control circuit. One end of the reset switch RESET is connected tothe junction of R₄ and C₅, the other end of the reset switch RESET isconnected to one junction of R₂ and C₆, which are connected in parallel.The other junction of R₂ and C₆ is connected to the gate pole of the SCRVD₅, R₃, and C₇. Capacitor C₇ is connected between the gate and cathodeof the SCR VD₅ to serve as a filter for preventing narrow noise pulsesfrom triggering the SCR VD₅. One end of the breaking switch K isconnected to the line terminal; the other end of K is connected to theload terminal. It is noted that the contact point between the breakingswitch K and the line terminal corresponds to the contact 103 of themovable contact holder, and the contact point between the breakingswitch K and the load terminal corresponds to the contact 101 of thefixed contact holder. The power supply of the control circuit isconnected to the line of the GFCI, so when the GFCI is energized, thecontrol circuit of the GFCI is also energized. When the reset switchRESET is closed, the capacitor C₆ is charged up, generating a triggersignal of about 20-40 ms to gate the SCR VD₅ into conduction.Consequently, the closing coil 73 is energized for a duration of about20-40 ms. That is, the closing coil 73 produces an electromagnetic forcefor about 20-40 ms to act on the plunger 75, sufficient to reset theGFCI.

The IC may be a special integrated circuit, for example, of type RV4145Aor RV2145.

As discussed above, capacitor C₄ is connected between the gate andcathode of the SCR VD₇ to serve as a filter for preventing narrow noisepulses from triggering the SCR VD₇. For additional protective purposes,the circuit shown in FIG. 10 also includes a metal oxide varistor (MOV)connected across the input terminals of the AC power source, in order toprotect the whole control circuit from transient voltage surges.

The test switch TEST and the current limiting resistor R₀ form the testcircuit. The current limiting resistor R₀ is connected to the powersource, and the other end of resistor R₀ is connected to the testswitch. The other end of the test switch TEST is connected to the otherend of the load. The test circuit constantly provides the GFCI an 8 mAfault current for periodically checking the working status of the GFCI.When the test switch is momentarily depressed, sufficient current willflow through the resistor R₀ to cause an imbalance in the currentflowing through the sensing transformers. This will simulate a groundfault condition, causing the amplifier and trip circuit to produce anoutput signal on the output terminal 5, which gates the SCR VD₇ intoconduction and thereby momentarily energizes the trip coil. Theresulting movement of the plunger causes the contacts to open, as willoccur during an actual ground fault condition.

Simultaneously, the GFCI receptacle also provides an indication circuit,where a current limiting resistor R₆ is connected in series with alight-emitting diode (LED) VD₆, and they are connected directly to theterminals of the load. When the reset button is depressed and the GFCIreceptacle is energized, the LED is illuminated. This affords a visualindication to the installer and the user that the GFCI receptacle is inthe normal conduction state.

If the GFCI receptacle is inadvertently miswired by connecting the lineto the load, before the breaking switch K closes, the control circuit isde-energized. Because the GFCI utilizes an electronically-controlledmeans for reset, when the control circuit is de-energized, the closingcoil can not be energized. In this manner, the closing coil can notproduce a corresponding electromagnetic force to act on the plunger,thereby keeping the GFCI also de-energized, achieving the reverse wiringprotection function.

In summary, the present invention provides a GFCI receptacle thatutilizes an electromagnetic tripper and an electronically-controlledmeans to control reset. This GFCI receptacle has reverse wiringprotection function and the advantages of, for example, tripping rapidlyand operating conveniently.

Recent changes in electrical standards have indicated the desirabilityof, instead of having a single fixed contact holder 100A or 100B (eachhaving a respective fixed contact 101) on each side conducting currentto/from the line, having a pair of fixed contact holders, one for theGFCI receptacle and one for the output load connection, for each side,phase and neutral, of the GFCI receptacle. By so doing, should the GFCIreceptacle be miswired, with the load side wires connected to thebinding screws for the line side, and vice versa, no current will beconducted into the GFCI receptacle (i.e., to a user load plugged intothe receptacle). The invention is adaptable to this type of arrangement,and FIGS. 11 and 12 depict embodiments of the invention that have sucharrangements.

In the embodiment shown in FIG. 11, which shows a side view of the GFCIin the tripped position, the single movable contact holder on each side(the view shown corresponds to the view shown in FIG. 7, so theequivalent movable contact holder in FIG. 7 is 102A) is replaced with amovable contact holder assembly 102A′. Movable contact holder assembly102A′ comprises two movable contact holder elements, 102A′-1 and102A′-2. Each of the movable contact holder elements 102A′-1 and 102A′-2has a V-shaped bend. Movable contact holder elements 102A′-1 and 102A′-2are arranged against each other at one end, as shown, with the V-shapedbends arranged opposite each other. At the end where they are arrangedagainst each other, the two movable contact holder elements 102A′-1 and102A′-2 electrically connected to a line-side conductor, which comesthrough the sensor assembly 80; alternatively, the two movable contactholder elements 102A′-1 and 102A′-2 may extend through the sensorassembly 80 and electrically connected (e.g., soldered) directly toprinted circuit board 90 to provide contact with the line-sideconductor. At the other end, each movable contact holder element,102A′-1 or 102A′-2, has a movable contact, 103A or 103B, respectively.The movable contacts 103A and 103B, as well as fixed contacts 101A and101B, may, for example, be riveted, soldered, or otherwise electricallyconnected to their respective contact holders, or they may, as a furtherexample, comprise conductive rivets.

As in the previous embodiments, the GFCI includes a movable bracket 79and a balance frame 77 mounted on the movable bracket 79. Alternatively,movable bracket 79 and balance frame 77 may be combined into a unitarystructure; while the remainder of this description is written under theassumption of separate components, it is equally applicable to theunitary design.

Balance frame 77 is equipped with a bracket 77A′ extending from eachside (see also, for example, FIG. 5). In this embodiment, however,bracket 77A′ has a somewhat different shape from bracket 77A as shown inFIG. 7. In particular, bracket 77A′ is shaped so as to be able toseparate movable contact holder elements 102A′-1 and 102A′-2, in thedirections of arrows B11 and C11, when bracket 77A′ is moved from pointa to point b, in the direction of arrow A11. The amount of separation ofmovable contact holder elements 102A′-1 and 102A′-2, when bracket 77A′is at point b, must be sufficient to cause movable contacts 103A and103B to make contact with fixed contacts 101A and 101B. As shown in FIG.11, the shape of bracket 77A′ may be as if a bracket 77A were fused to asecond bracket 77A that was flipped vertically, however, bracket 77A′may take any other suitable shape such that it fits between the V-shapedgrooves of movable contact holder elements 102A′-1 and 102A′-2 when inthe trip position (a) and such that it causes sufficient separation ofmovable contact holder elements 102A′-1 and 102A′-2 when in position b.Typical shapes of bracket 77A′ include a rounded trapezoidal shape, asshown in FIG. 11, and a rounded triangular shape.

In order to provide separate conductive paths on each side (neutral andphase) of the GFCI for conduction of electricity to/from the receptacleand to/from the output load conductor, fixed contact holders 100A and100B (as shown, e.g., in FIG. 4) are each split into two parts. This isdepicted conceptually in FIGS. 13A-13C, which show a split version offixed contact holder 100A. This is also depicted in the circuit diagramshown in FIG. 14, as part of switching apparatus K; the circuit of FIG.14 operates in a manner similar to that shown in FIG. 10, and will,therefore, not be further described (like parts have been labeled withidentical reference numerals). In particular, fixed contact holder 100Ais split into first contact holder component 100A-1, shown in FIGS. 13Aand 13B, and second contact holder component 100A-2, shown in FIG. 13C.In the depiction of FIGS. 13A-13C, the first contact holder component100A-1 is connected to an output load via binding screw 111. Firstcontact holder component 100A-1 includes a contact holder part 100A-1′,on which is situated fixed contact 101A. Second contact holder component100A-2 is shown connected to (one side of) an electrical outlet. Secondcontact holder component 100A-2 includes a contact holder part 100A-2′,on which is situated fixed contact 101B. First and second contact holdercomponents 100A-1 and 100A-2, including contact holder parts 100A-1′ and100A-2′, are shaped and oriented in a manner appropriate to theparticular embodiment and implementation of the invention (e.g., asshown in FIG. 11 or FIG. 12).

The sub-embodiment of FIG. 11 operates as follows. In the trippedposition, bracket 77A′ is located at point a, where it fits within theV-shaped grooves of movable contact holder elements 102A′-1 and 102A′-2.In this position, no contact is made between movable contacts 103A and103B and fixed contacts 101A and 101B, respectively. When the resetbutton 60 (see, e.g., FIG. 6) is pressed (assuming the absence of areverse wiring or other fault condition), the reset mechanism describedabove causes movable bracket 79 (and, hence, balance frame 77) to movealong the direction of arrow A11, which, in turn, causes bracket 77A′ tomove from point a to point b. This causes the ends of movable contactholder elements 102A′-1 and 102A′-2 having movable contacts 103A and103B, respectively, to separate (i.e., along the directions of arrowsB11 and C11, respectively). This, in turn, causes movable contacts 103Aand 103B to make contact with fixed contacts 101A and 101B, thuspermitting the conduction of current to/from, for example, an electricalappliance plugged into the GFCI receptacle and to/from an output loadterminal (e.g., binding screw 111, as shown, for example, in FIG. 3).

On the other hand, when bracket 77A′ is initially at point b and a fault(or test) occurs, movable bracket 79 (and balance frame 77, along withit) moves in the direction along arrow A11 so as to move bracket 77A′ topoint a. As a result, the ends of movable contact holder components102A′-1 and 102A′-2 bearing movable contacts 103A and 103B are no longerkept apart by bracket 77A′, which is now situated in the area formed bythe V-shaped bends in movable contact holder components 102A′-1 and102A′-2. As a result, contact between movable contacts 103A and 103B andfixed contacts 101A and 101B, respectively, is broken.

In the sub-embodiment shown in FIG. 12, the movable contact holder 102A″is mounted on a movable assembly 77′, which is the equivalent of movablebracket 79 and balance frame 77 of FIG. 4, but without any brackets 77A(and which may be of unitary construction), and is connected to aflexible conductor 122 at one end. The other end of the movable contactholder 102A″ is provided with the two movable contacts, 103A and 103B,which make contact with the two fixed contacts, 101A and 101B, when themovable assembly 77′ is in a first position (reached, e.g., by pressingreset button 60). The movable and fixed contacts do not make contactwhen the movable assembly 77′ is in a second (tripped) position, whichis what is depicted in FIG. 12. That is, the entire movable contactholder 102A″ is arranged to shift in the direction along arrow A12 whena condition causes movable assembly 77′ to shift in the direction alongarrow A12. Note that while FIG. 12 depicts, and this discussiondescribes, only one side of the apparatus, and thus only a singlemovable contact holder 102A″, there are actually two movable contactholders, one connected to each of two conductors (phase and neutral),both of which are mounted on movable assembly 77′.

Movable assembly 77′ is further equipped with a contact spring 121. Theforce provided by contact spring 121 serves to ensure good contactbetween movable contacts 103A and 103B and fixed contacts 101A and 101B.

As discussed above, movable assembly 77′ in FIG. 12 is the equivalent ofmovable bracket 79 and balance frame 77 of FIG. 4. As a result, movableassembly 77′ is coupled to and driven by plunger 75 in the same fashionas is movable bracket 79 in the embodiment of FIG. 4.

The sub-embodiment of FIG. 12 operates as follows. FIG. 12 shows themovable assembly 77′ in the tripped position (i.e., in its right-handposition along the direction of arrow A12 in FIG. 12). In this position,no contact is made between movable contacts 103A and 103B and fixedcontacts 101A and 101B, respectively. When the reset button 60 (see,e.g., FIG. 6) is pressed (assuming the absence of a reverse wiring orother fault condition), the reset mechanism described above causesmovable assembly 77′ to move along the direction of arrow A11, in theleft-hand direction in FIG. 12 (i.e., toward fixed contact holders100A-1 and 100A-2). This causes the movable contact holder 102A″ to moveas well. This, in turn, causes movable contacts 103A and 103B to makecontact with fixed contacts 101A and 101B, thus permitting theconduction of current to/from, for example, an electrical applianceplugged into the GFCI receptacle and to/from an output load terminal(e.g., binding screw 111, as shown, for example, in FIG. 3).

On the other hand, when movable assembly 77′ is initially in itsleft-hand position (as it would be following the operations in theprevious paragraph) and a fault (or test) occurs, movable assembly 77′moves in the right-hand direction along arrow A12, as shown in FIG. 12.As a result, movable contact holder 102A″ bearing movable contacts 103Aand 103B is moved in the right-hand direction, away from fixed contactholders 100A-1 and 100A-2. As a result, movable contacts 103A and 103Band fixed contacts 101A and 101B, respectively, are separated, andcontact is broken.

While the above discussion focuses on the specific implementation of thesub-embodiment of FIG. 12, it is apparent that variations are possible.For example, contact holder 102A″ need not cover or surround (part of)movable assembly 77′, as shown in FIG. 12. Contact holder 102A″ needonly be attached to movable assembly 77′ and provide movable contacts103A and 103B in a position for making contact with fixed contacts 101Aand 101B when movable assembly 77′ moves contact holder 102A″ into anappropriate position. For example, if movable assembly 77′ has a squaredshape, as shown in FIG. 12, contact holder 102A″ need only be aconductive plate on which movable contacts 103A and 103B are mounted,and contact with flexible conductor 122 may be provided by electricallyconnecting flexible conductor 122 to spring 121, which may be made of aconductive material and have a portion extending through a side or backof movable assembly 77′ to accommodate such electrical connection.Alternatively, spring 121 may be omitted, and the flexible conductor 122may be inserted through a hole in movable assembly 77′ to make contactwith contact holder 102A″, or some other type of electrical connection(e.g., a conductive post extending through the back of movable assembly77′) may be provided between contact holder 102A″ and flexible conductor122.

Furthermore, movable assembly 77′ may take on numerous shapes and forms.As discussed above, it may be of unitary form, and both movable contactholders (for the phase and neutral sides) may be mounted on it.Additionally, for example, movable assembly 77′ may have a base portioncoupled to the plunger from which extend two supports, on each of whichis mounted one of the movable contact holders. Movable assembly 77′ may,alternatively, comprise a phase side movable assembly and a neutral sidemovable assembly, both of which are coupled to, and move with, theplunger.

Flexible conductor 122 may comprise a pair of conductors (e.g., twomutually insulated wires) together (one for phase and one for neutral),or there may be two flexible conductors, where flexible conductor 122,as shown in FIG. 12, would be one of them. In the conductive contactspring implementation, for example, as discussed above, each flexibleconductor, or each of the conductors within the flexible conductor,would be electrically connected to one of the two contact springs.

FIG. 15 depicts a variation on the sub-embodiment shown in FIG. 12. Inthis variation, the flexible conductor 122 is split into two portions,both of which are electrically connected to a line-side conductor. Forexample, in the specific implementation shown, a conductive assembly123, which may, for example, comprise copper, extends through sensorassembly 80, and the two portions of flexible conductor 122 are coupled(e.g., soldered or otherwise coupled) to conductive assembly 123.Alternatively, the two portions of flexible conductor 122 may be dualextensions of conductive assembly 123.

In the variation of FIG. 15, the movable contact holder 102A″ of FIG. 12is split into two portions, similar to the sub-embodiment of FIG. 11,denoted 102A′-1 and 102A′-2. Each of movable contacts 103A and 103B iselectrically coupled to a respective one of the movable contact holderportions 102A′-1 and 102A′-2. Movable contact holder portions 102A′-1and 102A′-2 are shown extending through movable assembly 77′, and eachis electrically connected to the one of the respective portions offlexible conductor 122. Movable contact holder portions 102A′-1 and102A′-2 may include projections that prevent them from becomingdislodged from movable assembly 77′. In conjunction with the two movablecontact holder portions, contact spring 121 is shown as being replacedby two contact springs, 121A-1 and 121A-2, each of which helps maintaincontact between a respective one of movable contacts 103A and 103B and arespective one of the fixed contacts 101A and 101B. In an alternativeembodiment (not shown), a single, non-conducting contact spring may beused to help maintain contact between both pairs of movable and fixedcontacts. The operation of this variation of the sub-embodiment of FIG.12 is substantially as described for the sub-embodiment of FIG. 12.

While only the fundamental features of the present invention have beenshown and described, it will be understood that various modificationsand substitutions and changes of the form and details of the devicedescribed and illustrated and in its operation may be made by thoseskilled in the art, without departing from the spirit of the invention.

1. (canceled)
 2. A ground fault circuit interrupter (GFCI), comprising aswitching mechanism, wherein the switching mechanism comprises: twopairs of fixed contact holders, each member of each pair having at leastone fixed contact at one end; a pair of movable contact holders, eachhaving an end having two or more movable contacts, each movable contactbeing arranged for contacting a respective one of the fixed contacts;and a movable assembly that moves between a first position in which eachfixed contact makes contact with the respective movable contact and asecond position in which the fixed contacts are separated from themovable contacts, the movable assembly causing movement of the pair ofmovable contact holders when it moves between the first and secondpositions.
 3. The ground fault circuit interrupter as claimed in claim2, further comprising: an electromagnetic resetting component, which,when energized, causes the movable assembly to be in the first position;an electromagnetic tripping component, different from theelectromagnetic resetting component, which, when energized, causes themovable assembly to be in the second position; and a control circuit,which, upon detection of a fault condition, energizes theelectromagnetic tripping component, and which is responsive to a resetcondition for energizing the electromagnetic resetting component.
 4. Theground fault circuit interrupter as claimed in claim 3, wherein thecontrol circuit is de-energized upon detection of a fault condition,thus rendering the ground fault circuit interrupter inoperative.
 5. Theground fault circuit interrupter as claimed in claim 2, wherein themovable assembly comprises: a plunger partially disposed within anelectromagnetic assembly and being able to move back and forth undermagnetic force; and a sub-assembly connected to and driven by theplunger disposed to move along an axial line of the plunger between thefirst position and the second position, movement of the sub-assemblycausing movement of the pair of movable contact holders when thesub-assembly moves between the first and second positions. 6-10.(canceled)
 11. The ground fault circuit interrupter as claimed in claim5, wherein the movable contact holders are mounted on the movableassembly. 12-16. (canceled)
 17. The ground fault circuit interrupter asclaimed in claim 2, wherein each of the pair of fixed contact holderscomprises: a first fixed contact holder having a fixed contact and beingelectrically coupled to a prong of an electrical outlet; and a secondfixed contact holder having a fixed contact and being electricallycoupled to a load output.
 18. A ground fault circuit interrupter (GFCI)comprising: a housing; a pair of movable contact holders, each disposedat least partially within the housing between a line side and a loadside, each of the movable contact holders comprising two movable contactholder components, wherein each of the movable contact holdersterminates at a first connection capable of being electrically connectedto a source of electricity, a second connection capable of conductingelectricity to at least one load, and a third connection capable ofconducting electricity to at least one user accessible load; two pairsof fixed contact holders, each of the fixed contact holders having atleast one contact and capable of being electrically connected, throughthe at least one contact, to a corresponding movable contact holder; acircuit interrupting portion disposed within the housing and configuredto cause electrical discontinuity between the line side and the loadside upon the occurrence of a predetermined condition; and a resetportion disposed at least partially within the housing and configured toreestablish electrical continuity between the line side and the loadside.
 19. A ground fault circuit interrupter (GFCI) comprising: ahousing; a phase conductive path and a neutral conductive path, eachdisposed at least partially within the housing, between a line side anda load side, wherein each of the phase conductive path and the neutralconductive path comprises: a pair of movable contact holders; and atleast one flexible conductor electrically coupled to the pair of movablecontact holders and electrically coupled to an external electricalconnection; wherein the phase conductive path terminates at a firstconnection capable of being electrically connected to a source ofelectricity, a second connection capable of conducting electricity to atleast one load, and a third connection capable of conducting electricityto at least one user accessible load, and wherein the neutral conductivepath terminates at a first external connection capable of beingelectrically connected to a source of electricity, a second connectioncapable of conducting electricity to at least one load, and a thirdconnection capable of conducting electricity to at least one useraccessible load; two pairs of fixed contact holders, each fixed contactholder having at least one fixed contact through which the fixed contactholder is capable of being electrically connected to a correspondingmovable contact holder; a movable assembly on which the movable contactholders are mounted; four contact springs, each mounted at leastpartially within the movable assembly and abutting against one of themovable contact holders to provide a contact force to aid contactbetween a movable contact mounted on a movable contact holder and acorresponding fixed contact; a circuit interrupting portion disposedwithin the housing and configured to cause electrical discontinuitybetween the line side and the load side upon the occurrence of apredetermined condition; and a reset portion disposed at least partiallywithin the housing and configured to reestablish electrical continuitybetween the line side and the load side.